Abstract
<jats:p>Lipid peroxidation, the radical-chain oxidation of membrane lipids, terminates in part through spin-selective encounters between lipid-peroxyl radicals. We ask how far a shaped magnetic field can steer this branch under spin relaxation and how that change propagates to the oxidation flux. Gradient-projection and bang–bang Pontryagin controls were evaluated with a stochastic-Schrödinger treatment of dipolar fluctuations and an independent Brownian-dynamics model. A best-found dipolar-scale field raises the triplet-initialised singlet termination yield from ΦS|T = 0.220 at 50 µT to 0.562 (+155%), with the bang–bang solution corroborating at 0.522; a bandwidth-filtered proxy retains 0.270. Under Brownian dynamics the control advantage remains positive throughout the sampled rotational-correlation-time range, and one field transfers across eight microdomain-size–diffusion parameter sets. Closing the spin calculation to classical autoxidation kinetics gives Ceff = −f/(1+f), where f is the fraction of peroxyl loss proceeding through bimolecular termination. Two limiting descriptions of the productive encounter population bracket the predicted suppression of oxidation flux in antioxidant-free liposomes at approximately 21–37%, and at approximately 4–10% for the bandwidth-filtered field. α-Tocopherol attenuates the response as interception comes to dominate, providing an internal experimental control. These values describe an elementary encounter and a minimal kinetic model, not whole-cell lipid peroxidation.</jats:p>